An experimental study of the creep mechanical properties of unsaturated soil and empirical models

In order to predict the effect of matrix suction on the creep behavior of unsaturated silty clay, the empirical model of unsaturated creep is established. Based on the unsaturated creep test of silty clay, the Mesri model and Log-Modified model are improved. The stress-strain relationships of the Mesri model and Log-Modified model are described with a hyperbolic function. The relationship between stress-matrix suction and strain is established by the initial tangent modulus, and the relationship between stress-matrix suction and strain is obtained. The strain-time relationship of the Mesri model and the Log-Modified model are described with the power function and the three-parameter power function, respectively, and the modified Mesri model and the Log-Modified model are obtained. The two improved models are stress-matrix suction-strain-time models. The parameters of the stress-matrix suction-strain relationship are obtained by fitting the ε/D-ε relation curve with the power relation. According to the lnε-lnt relation, the strain-time relationship parameters of the improved Mesri model are determined, and the BFGS algorithm and the general global optimization method are used to solve the strain-time relationship parameters of the improved Log-Modified model. The relational parameters are replaced by two improved models, and the corresponding unsaturated creep empirical models are obtained. The unsaturated creep curves are identified and the prediction accuracies of the two improved models are compared. The results show that the prediction effect of the improved Log-Modified model is poor, and the improved Mesri model can accurately describe the creep characteristics of the unsaturated silty clay.